acl_extended_fd man page
acl_extended_fd — test for information in the ACL by file descriptor
Linux Access Control Lists library (libacl, -lacl).
The acl_extended_fd() function returns
1 if the file identified by the argument fd is associated with an extended access ACL. The function returns
0 if the file does not have an extended access ACL.
An extended ACL is an ACL that contains entries other than the three required entries of tag types ACL_USER_OBJ, ACL_GROUP_OBJ and ACL_OTHER. If the result of the acl_extended_fd() function for a file object is
0, then the ACL defines no discretionary access rights other than those already defined by the traditional file permission bits.
Access to the file object may be further restricted by other mechanisms, such as Mandatory Access Control schemes. The access(2) system call can be used to check whether a given type of access to a file object would be granted.
If successful, the acl_extended_fd() function returns
1 if the file object identified by fd has an extended access ACL, and
0 if the file object identified by fd does not have an extended access ACL. Otherwise, the value
-1 is returned and the global variable errno is set to indicate the error.
If any of the following conditions occur, the acl_extended_fd() function returns
-1 and sets errno to the corresponding value:
The fd argument is not a valid file descriptor.
The file system on which the file identified by fd is located does not support ACLs, or ACLs are disabled.
This is a non-portable, Linux specific extension to the ACL manipulation functions defined in IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned).
access(2), acl_get_fd(3), acl(5)